Environmental sounds typically comprise a mixture of various sound wave frequencies having varying intensities. Repeated or prolonged exposure of human ears to environmental sounds of sufficiently high sound pressure levels can cause temporary or permanent hearing loss. For example, noises resulting from explosions or bursts often comprise sound wave frequencies that can be in both relatively high and low frequency bands and can have an intensity sufficient to cause hearing problems.
Individuals who are frequently exposed to sounds of dangerous frequencies and intensities run the risk of incurring hearing loss or even deafness. These individuals include workers at demolition or construction sites, operators of noisy equipment, and personnel in active military service. Ear (that is, hearing) protection devices are often desired to reduce or prevent a loss in hearing acuity and the gradual increase in the threshold of hearing that can result from extended exposure to loud noise.
Various sound attenuation devices are known that specifically address this problem. These include conventional earplug devices, earmuff devices, and the like, which function to reduce the negative effects of noise exposure by limiting the entry of sound waves into the ear. Earmuff devices can be preferred over earplug devices, due to their greater ease of intermittent use (where repeated insertion and removal of earplugs would be annoying or impractical) and/or superior comfort (for example, due to the use of soft ear cushions and the absence of items inserted into the ear).
Conventional earmuff devices generally include a pair of rigid earcups connected by a head band, with foam padding inside the earcups (for sound absorption) and around the rims of the earcups (for comfort and acoustic sealing). In order to obtain a perceptible and effective level of sound attenuation, the foam padding is generally fairly thick (for example, about 1-2 centimeters thick). This adds bulk or volume, as well as mass or weight, to the earmuff device, further necessitating thick-profile, large earcups and a resulting larger and heavier earmuff device that can be inconvenient and/or uncomfortable (for example, hot and sweat-inducing) for the wearer. This has often led to a lack of compliance with hearing protection guidelines and/or regulations and to resulting hearing damage.
Furthermore, in some environments (for example, extremely loud industrial or manufacturing plants, construction or demolition sites, and the like), very high sound attenuation can be desired from earmuff devices. Numerous attempts to increase earmuff sound attenuation have been made, including, for example, reducing acoustic leaks through or around earcups, increasing the mass and/or volume of the earcups, increasing head band tension, and minimizing resonating surfaces such as flat surfaces. These attempts have been at least somewhat successful in increasing sound attenuation, but the resulting earmuff devices have been heavier, larger, more difficult to put in place, and/or generally less comfortable than the original earmuff devices, as well as often unacceptably attenuating desirable acoustic frequencies (for example, the relatively high frequencies of human speech, warning signals, and the like) along with (or even to a greater extent than) undesirable acoustic frequencies.